A large variety of load bearing platforms are used in industry to transport goods from on place to another or to serve as mobile instrument or tool stations and the like. Such platforms are typically supported upon casters or wheel assemblies, either fixed or swiveling, to provide a rolling support for the platforms.
A problem frequently faced in the use of such platforms is the tendency for wheels to drag when encountering small obstacles such as construction debris, uneven floor or sidewalk joints, and the like. That problem is particularly acute with platforms used in work environments in which the platform must cross electrical cords or pneumatic hoses that power other equipment. Further, cargo carrying platforms are sometimes loaded beyond their safe capacity, thus creating another hazardous condition.
There are a number of different wheel assemblies in the prior art that propose to address those problems. For example, wheel assemblies that include a primary wheel carrying a plurality of smaller, secondary wheels are shown in U.S. Pat. No. 3,208,544 to Colvin; U.S. Pat. No. 1,326,679 to Macbeth et al; U.S. Pat. No. 795,620 to Jones; and U.S. Pat. No. 722,433 to Ritchie. Wheel assemblies employing braking means used in association with walkers are described in U.S. Pat. No. 6,068,273 to Rao et al; in U.S. Pat. No. 5,112,044 to Dubats; and in U.S. Pat. No. 5,020,560 to Turbeville.
The wheel assemblies described in the cited prior art do not satisfactorily address the needs for wheel assemblies that surmount small obstacles without wheel drag, and prevent overloading of a mobile platform. This invention fills that need.